Forum: Ruby LISP to Ruby translation

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Douglas L. (Guest)
on 2005-12-15 04:36
(Received via mailing list)
Jut a quick one, how do you translate this:

((if (zero? 0) + -) 3 4)
=> 7

to Ruby?

Cheers,
Douglas
Joel VanderWerf (Guest)
on 2005-12-15 04:46
(Received via mailing list)
Douglas L. wrote:
> Jut a quick one, how do you translate this:
>
> ((if (zero? 0) + -) 3 4)
> => 7
>
> to Ruby?
>
> Cheers,
> Douglas
>

3.send(x.zero? ? :+ : :-, 4)

It's a little hard to read with all those colons. Maybe this is better:

3.send(if x.zero? then :+ else :- end, 4)

Or you could replace symbols with strings for readability, at a cost to
speed:

p 3.send(x.zero? ? "+" : "-", 4)
Neil S. (Guest)
on 2005-12-15 04:49
(Received via mailing list)
Douglas L. wrote:
> Jut a quick one, how do you translate this:
>
> ((if (zero? 0) + -) 3 4)
> => 7
>
> to Ruby?

Well, these kind of questions are rarely helpful; translating an
idiomatic expression out of context from one language is often useless,
because in a greater context the ruby code might be doing something
completely different to begin with.

But, if you want a one-liner...

3.method(0.zero? ? :+ : :-).call(4)

--
Neil S. - removed_email_address@domain.invalid

'A republic, if you can keep it.' -- Benjamin Franklin
Mark J.Reed (Guest)
on 2005-12-16 00:24
(Received via mailing list)
Douglas L. wrote:
> Just a quick one, how do you translate this:
>
> ((if (zero? 0) + -) 3 4)

What dialect of LISP is that?  Not Common... CL has no "zero?"
(it's "zerop"), and + and - refer to input history rather than the
functions
associated with the operators.  To do something like that in CL I think
you have to use the characters '+ and '- and an (eval)...
Edward F. (Guest)
on 2005-12-16 00:40
(Received via mailing list)
On Fri, Dec 16, 2005 at 07:22:39AM +0900, Mark J.Reed wrote:
> Douglas L. wrote:
> > Just a quick one, how do you translate this:
> >
> > ((if (zero? 0) + -) 3 4)
>
> What dialect of LISP is that?  Not Common... CL has no "zero?"

It's Scheme.  A much nicer dialect than CL, IMHO.  ;-)

I think in CL the equivalent would be:

((if (zerop 0) #'+ #'-) 3 4)

Note the ugly sharp-quotes, due to the fact that CL has separate
namespaces for values and functions.

regards,
Ed
Stephen W. (Guest)
on 2005-12-16 09:12
(Received via mailing list)
On Dec 14, 2005, at 6:36 PM, Douglas L. wrote:

> ((if (zero? 0) + -) 3 4)
> => 7
>
> to Ruby?

7 if true

--Steve
Joel VanderWerf (Guest)
on 2005-12-16 09:27
(Received via mailing list)
Stephen W. wrote:
>
> --Steve
>

7
Martin DeMello (Guest)
on 2005-12-16 12:04
(Received via mailing list)
Joel VanderWerf <removed_email_address@domain.invalid> wrote:
> > 7 if true
> >
> > --Steve
>
> 7

There - who says ruby isn't concise!

martin
Christian N. (Guest)
on 2005-12-17 01:31
(Received via mailing list)
Edward F. <removed_email_address@domain.invalid> writes:

> I think in CL the equivalent would be:
>
> ((if (zerop 0) #'+ #'-) 3 4)

No, you need:

  (apply (if (zerop 0) #'+ #'-) '(3 4))

> Note the ugly sharp-quotes, due to the fact that CL has separate
> namespaces for values and functions.

And that is why. :-)
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